1. Field of the Invention
The present invention relates to tool bits for use on electric tools.
Accordingly the present invention relates more particularly to rotary tools that are adapted to receive their rotational forces from the shank portions of tool bits used on electric tools without chucks.
2. Cross References and Related Applications
The applicant of the present invention has filed on Dec. 18, 1980 an application of an invention entitled: "Elements for a Tool System" carrying Ser. No. 217,798 now U.S. Pat. No. 4,413,937 and on Aug. 23, 1982 an application for an invention entitled "Screw Drill Adjustable for Various Sizes" and is filing on the filing date of this invention another application for a "Method and Apparatus for Securing Combination Tools". All these applications although differing in function and structure from the present invention deal with tools used in electric- and hand tools.
3. Description of the Prior Art
In the use of electric hand tools such as drills, the operation in one location often entails multiple operations such as drilling, counterboring a pilot hole and finally driving a fastener into the hole. It is very efficient workpractice to do these operations with a single machine, and the present invention provides accordingly slide-on tools to be secured temporarily onto the shank portion of the tool bit used already in the machine. The invention of the applicant with Ser. No. 217,798 now U.S. Pat. No. 4,413,937 and known by the Trademark CHUCK-MATE enables the operator of such an electric drill to insert a three-pronged rotary tool over the tool bit which might have a round shank into the chuck of the machine. In this system, rotational forces are transmitted to the rotary tool by way of the sides of the pronges from the sides of the jaws of the said chuck. However, many craftsmen use in addition to a chuck-equipped drill an electric screw-driver which has ratchet means and depth-stopping means but in most cases has no chuck. Another means to drive a tool bit from another was taught by Smith in U.S. Pat. No. 3,973,784 where a hexagonal cavity is used to pick up the rotation that via a hand-held free-wheeling handle is guided and transmitted to the rotary tool. The present invention differs in function and structure from the Smith device in these important aspects: The present invention becomes temporarily attached to the machine used and requires no guidance by the free hand of the operator, and needs therefore no guiding sleeve. The means to take off torque from the shank portion of the tool bit in the machine is not a fixed-dimension cavity but is made of many members, self-adjusting and has compression means. It offers therefore significant improvement over the Smith device.